953 resultados para Dames, Michael


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Michel Bauwens es filósofo, consultor de Internet y teórico de las redes peer to peer (P2P). Fundador de la Foundation fo P2P Alternatives, director de la revista Wave y editor del conocido newsletter Pluralities-Integration, en esta conversación nos avanza algunas de las consecuencias profundas que están acarreando- y podrán acarrear en el futuro- las recientes innovaciones tecnológicas y sociales asociadas con el P2P.

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Primary amine-guanidines derived from trans-cyclohexane-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of isobutyraldehyde to arylated and heteroarylated nitroalkenes. The reaction was performed in the presence of imidazole as the additive in aqueous DMF as the solvent at 0 °C. The corresponding Michael adducts bearing a new stereocenter were obtained in high yields and with enantioselectivities of up to 80%. Theoretical calculations are used to justify the observed sense of the stereoinduction.

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Simple and commercially available chiral 1,2-diamines were used as organocatalysts for the enantioselective conjugate addition of aldehydes, including α,α-disubstituted, to maleimides. The reaction was carried out in the presence of hexanedioic acid as an additive in aqueous solvents at room temperature. By employing (1S,2S)- and (1R,2R)-cyclohexane-1,2-diamine as organocatalysts, the corresponding Michael adducts bearing new stereocenters were obtained in high or quantitative yields with enantioselectivities of up to 92%, whereas the use of (1S,2S)-1,2-diphenylethane-1,2-diamine gave a much lower ee. Theoretical calculations were used to justify the observed sense of the stereoinduction.

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The monoguanylation of (1S,2S)- and (1R,2R)-cyclohexane-1,2-diamine affords chiral primary amine-guanidines that are used as chiral organocatalysts in the enantioselective Michael addition of aldehydes, particularly α,α-disubstituted aldehydes, to maleimides. The reaction is carried out in the presence of imidazole, as an additive, in aqueous N,N-dimethylformamide, as the solvent, and affords the corresponding enantioenriched succinimides in high or quantitative yields with enantioselectivities up to 96 % ee. Theoretical calculations (DFT and M06–2X) suggest a different hydrogen-bonding coordination pattern between the maleimide (C=O) and the catalyst (NH groups) is responsible for the enantioinduction switch that is observed when the reaction is carried out using primary amine-guanidines versus primary amine-thioureas as the organocatalysts.

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A wide variety of chiral succinimides have been prepared in high yields and enantioselectivities by asymmetric conjugate addition of 1,3-dicarbonyl compounds to maleimides under very mild reaction conditions using a bifunctional benzimidazole-derived organocatalyst. Computational and NMR studies support the hydrogen-bonding activation role of the catalyst and the origin of the stereoselectivity of the process.

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Enantiomerically pure mono-N-Boc-protected trans-cyclohexa-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to maleimides. Using a single enantiomer of the organocatalyst, both enantiomeric forms of the resulting Michael adducts bearing a new quaternary stereocenter are obtained in high yields, by only changing the reaction solvent from chloroform (up to 86% ee) to aqueous DMF (up to 84% ee).

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Four letters discussing news of friends and domestic politics and the presidential election, in addition to trade and purchases of certain goods.

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Four letters regarding unrest in Chile, the election of Vice President Joaquín Vicuña and inception of the Chilean Civil War, and subsequent events related to the war.

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In this deed of feoffment, written on Dec. 10, 1677, Thomas Sweetman agreed to sell his dwelling house, barn, and orchard to his son-in-law, Michael Spencer, for the cost of eighty pounds sterling. The property was located in Cambridge, Massachusetts, on what was then the northwest corner of the grounds of Harvard College, and was sold "together with the wood lot upon the rocks and cow commons belonging to it." The deed specifies that both Sweetman and his wife Isabel were to be allowed to occupy the property until their deaths, and further explains that Spencer and his family were already living in the dwelling house, occupying three rooms. The document was signed, sealed, and delivered in the presence of Daniel Gookin, Jr. and John Bridgham. It was also signed by Thomas Sweetman.